The present invention relates to a hybrid vehicle, and more specifically to a hybrid vehicle driven by an internal combustion engine, a single combined motor/generator and a compound planetary-gear transmission.
Hybrid vehicle is one kind of vehicle that combines both internal- combustion engine and electrical motor as power source or driving unit. There are several types of hybrid vehicle that have been proposed. One of them is the series type of hybrid vehicle basically driven by electric motors with the electrical power generated from an internal-combustion engine. Another is the parallel type of hybrid vehicle driven by both an internal-combustion engine and an electric motor with the electrical power drawn from off-board electrical source, not from the internal- combustion engine. Furthermore, there are various compound types of hybrid vehicle whose characteristics are somewhat combined with those of the series and parallel type of hybrid vehicle. The major differences among the varieties of compound-type hybrid vehicle are related to their layout on power train and design on control strategy thereof.
In particular, one compound type of hybrid vehicle uses a driving motor, an internal-combustion engine and a generator connected through a differential gear. With this arrangement, the vehicle can be started from stop by the driving motor alone, and driven by both the driving motor and engine when it is driven beyond a specific vehicle speed. A portion of the driving power from the engine is generated into electric power for recharging an energy storage device or driving an electric motor. Additionally, the operating speed range of the engine can be controlled by the generator through the action of the differential gear. In consequence, the engine can be operated at a full load and a highly efficient range for better fuel economy and emission reduction.
However, since the engine and the generator are connected through a differential gear unit, the respective rotational speed and torque are mutually related. Therefore, in order to maintain fill throttle operation of the engine and fulfill various driving conditions, the generator is inevitably subjected to high generation load. This may cause high energy conversion loss and undesirable high charging load of the battery pack. Furthermore, the driving motor may be operated at high operating speed and low efficient range when the vehicle is cruising at a high speed range. The complexity of the compound-type hybrid vehicle including one electric motor and one generator, accompanied with a driver, also results in undesirable high manufacturing cost and more energy loss arising from additional weight and heat loss of power electronics.
Therefore, the present invention provides an improved hybrid vehicle for overcoming the problems described above.
It is, therefore, a primary object of the present invention to provide a hybrid vehicle which is capable of fulfilling vehicle staring and complex driving requirement by using one combined motor/generator, not separately one generator and one motor.
It is the second object of the present invention to provide a hybrid vehicle having an overdrive ratio for the motor/generator in the forward direction. The hybrid vehicle according to the present invention can prevent the motor/generator from operating at an undesirable high-speed and low-efficiency range when the vehicle is mainly driven by the engine.
It is the third object of the present invention to provide a hybrid vehicle which can reduce the generating load for the motor/generator as well as the charging load for the battery in the forward direction.
It is the fourth object of the present invention to provide a hybrid vehicle capable of switching among different operation modes by simply controlling the motor/generator and engine with or without operating the clutches.
It is the fifth object of the present invention to provide a hybrid vehicle capable of being smoothly started and driven at a low-speed range by the motor/generator alone and with the engine being off.
It is the sixth object of the present invention to provide a hybrid vehicle which can switch from a motor-driven mode to an engine-driven mode by simply turning the engine on and the motor/generator off with or without any clutch operation.
It is the seventh object of the present invention to provide a hybrid vehicle which can modulate the driving torque output from the engine to assist a required acceleration by controlling the torque output of the motor/generator in the forward direction.
It is the eighth object of the present invention to provide a hybrid vehicle which can distribute a portion of the driving power outputted from the engine to recharge the energy storage device, such as battery or ultracapacitor etc.
It is the ninth object of the present invention to provide a hybrid vehicle which can control the rotational speed of the engine through the differential action of the compound planetary-gear set by controlling the rotational speed of the motor/generator.
It is the tenth object of the present invention to provide a hybrid vehicle which can fulfill the required driving performance with a decreased throttle application and a narrowed operating speed range of the engine such that the maximum fuel economy and considerable emission reduction can be gained.
It is the eleventh object of the present invention to provide a hybrid vehicle which can turn off the engine during the period of decelerating, driving downhill and motor-driven mode at a low speed or stop, thereby reducing the unwanted fuel consumption and emission caused by the part-load operation of the engine.
It is the twelfth object of the present invention to provide a hybrid vehicle which can provide a large reduction ratio for the motor/generator in the reverse direction, thereby supplying sufficient drive torque for starting the vehicle at low speed mode.
It is the thirteenth object of the present invention to provide a hybrid vehicle which can be operated in various forward modes and one reverse mode with one compact and efficient planetary-gear set.
It is the fourteenth object of the present invention to provide a hybrid vehicle which can provide regenerative braking if the clutches are controllable.
According to the present invention, the hybrid vehicle includes an engine, a starter, a motor/generator, a driving shaft, a compound planetary-gear device and a vehicle control device. The starter is used for starting said engine. The motor/generator is operated in both generator mode and motor mode in a reverse direction as well as in a forward direction. The driving shaft is connected with driving wheels through reduction gears. The compound planetary-gear device is connected to the motor/generator, the engine and the driving wheels through the driving shaft and the reduction gears. The vehicle control device is used for powering the hybrid vehicle by the motor/generator alone when a vehicle speed detected by a vehicle speed detection device is below a predetermined switching vehicle speed, and for starting the engine by the starter as well as turning off the motor/generator when the vehicle speed reached the predetermined switching vehicle speed, and for modulating an output driving torque by controlling a torque and a speed of the motor/generator.
Preferably, the compound planetary-gear device includes a first planetary-gear set and a second planetary gear set. The first planetary gear set includes a first sun gear, a first annulus gear and a plurality of first planetary gears mounted on a first carrier, and the second planetary- gear set is interconnected to the first planetary-gear set. The second planetary-gear set includes a second sun gear, a second annulus gear and a plurality of second planetary gears mounted on a second carrier. The first sun gear is fixed to ground, the first carrier is interconnected with the second sun gear and said motor/generator, and the second carrier is connected to the engine.
Preferably, the hybrid vehicle further includes a dual-drive clutch, a dual-drive shaft and a locking clutch. The dual-drive clutch is selectively used to engage or disengage the connection between the first annulus gear and the second annulus gear. The dual-drive shaft is connected with the first annulus gear device and the driving shaft through the dual-drive clutch. The second annulus gear is selectively connected to the dual-drive shaft and the first annulus gear device through the dual-drive clutch and is connected to the driving shaft. The locking clutch is selectively used to lock a shaft connected between the second carrier and the engine to ground.
In accordance with an aspect of the present invention, when the motor/generator drives the driving wheels in reverse direction and the engine is off, the locking clutch is locked to ground.
In accordance with another aspect of the present invention, when the engine is started by the starter to serve as a main driving source of the hybrid vehicle, the motor/generator is off and the vehicle speed reaches the predetermined switching vehicle speed, the locking clutch is unlocked.
In accordance with another aspect of the present invention, when the motor/generator is at a driving mode in forward direction and both the motor/generator and the engine can drive the hybrid vehicle through both the dual-drive shaft and the driving shaft, the dual-drive clutch is locked.
In accordance with another aspect of the present invention, when the motor/generator is at a generator mode in forward direction and a generator load thereof is insufficient to release the dual-drive clutch from a locking condition, the dual-drive clutch is locked.
In accordance with another aspect of the present invention, when the motor/generator is at a generator mode in forward direction and serves to generate electric power to recharge an energy storage device, the rotational speed of the engine is controlled by adjusting the rotational speed of the motor/generator through a differential action of the second planetary-gear set, and the hybrid vehicle is solely driven by the engine through the driving shaft, the dual-drive clutch is unlocked.
The vehicle according to the present invention is smoothly started by the motor/generator with driving torque output in reverse direction. When vehicle speed reaches an engine starting speed, the engine is started by a starter. As the engine is ignited, the vehicle is mainly driven by the engine. The motor/generator serves to modulate the output torque from the engine in response to the acceleration or deceleration of the vehicle. In this way, it is possible to effect the desired acceleration with decreased throttle application in order to provide maximum economy of operation and to achieve the desired emission reduction.
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: